It's Actually Common To Find Your Square Is Out Of Square

Very few square are adjustable allowing for calibration.

Framing squares can go out of square if they are dropped too many times. The trick to ajusting a framing square is to punch some dimples with a center punch at the intersection of the two blades along the line between the two corners.  The center punch marks should be grouped closer to the inside corner or the outside corner depending on where you want expand the metal to change the angle slightly between the two blades.

If your speed square is out of square you could file one or both sides till it is square.

With some squares there is no way to adjust them. It's better to scrap the square and go buy a better quality square square.

In this video starting with a perfectly straight edge, you are shown how to draw two lines with your square. If the lines are perfectly parallel then your square is true.